In particular, but in a non-limiting manner, the invention relates to monitoring signals emitted by certain tracers used in robot systems for checking the dimensions of metal parts of various shapes. It relates especially and quite directly to zero-contact-pressure tracers or feelers, that is, those in which there is no physical contact with the part to be checked, such as the tracer for which French patent application No. 80 25457 was filed on Dec. 1, 1981 by the Commissariat a l'Energie Atomique [French Atomic Energy Commission].
The electrical signal emitted by a tracer of this type is a direct current or alternating current voltage which at certain instants can vary rapidly about its nominal value and can exhibit significant phenomena which need to be reliably detected in the presence of the influence of stray electricity which may be present.
In particular, the electrical voltage established in robot systems between a tracer and the part to be tested undergoes rapid high frequency variations when the tracer approaches quite near the position of contact with the part. These variations, in turn, translate into major variations in the electrical field between the tracer and the part, which are characteristic of the approach toward the part; it is these variations that need to be precisely and reliably detected by isolating them, especially from any background or stray noise.